Page 347 - Beyond Decommissioning

Case studies of nuclear redevelopment 323

7.11 Dounreay Site Remediation, United Kingdom

The 55-ha Dounreay site in Caithness, Scotland has been the UK center for fast reactor
research and development since 1955. It hosed a materials test reactor (MTR) and two
demonstration fast reactors—the Dounreay Fast Reactor (DFR) and the Prototype Fast
Reactor (PFR)—as well as nuclear fuel reprocessing and fabrication. It also supported a
number of nuclear applications resulting in a range of nuclear and nonnuclear legacies
including exotic fuels for conditioning and disposal, contaminated alkali metals, his-
toric intermediate-level waste (ILW) and LLW disposal sites, and liquid ILW from
three different nuclear fuel cycles. In 1988, the UK Government decided to terminate
the fast reactor program and the last reactor (PFR) shutdown in 1994. Since 2000, the
site has focused only on decommissioning programs.
Site decommissioning and remediation work is well underway with more than 100
buildings already demolished. The dedicated LLW repository for Dounreay solid
waste, adjacent to the nuclear site, receives operational and demolition wastes. The
key milestones of the strategy implementation are mostly related to fuel disposition
from the Dounreay site, liquid raffinate immobilization to minimize the mobile haz-
ard, shaft and silo emptying of ILW, demolition of reactors, and fuel handling plants
followed by a realistic level of land remediation to take the site to an IES by 2033. The
IES is the envisaged final shutdown of the site and cessation of physical work until the
final SES (Dounreay, 2017a).
Dounreay Site Restoration Limited (DSRL) is the SLC responsible for the activ-
ities at Dounreay site. The current PBO is Cavendish Dounreay Partnership (CDP)
Limited, a consortium comprising Cavendish Nuclear Limited, CH2M Hill and
URS. Note: A thorough description of the UK’s regime for decommissioning and site
remediation in given in Office for Nuclear Regulation (2015). See also Glossary
definitions.
The strategy implementer DSRL continues to deliver the program with the aim at
reaching the defined IES by 2030–33 under a target cost closure contract. The mission
of immediate decommissioning to an IES has seen periodic increases in the scope of
work. These changes have resulted from increased security requirements and a change
in the management of spent exotic fuels. The changes have not altered the fundamen-
tal strategy of risk reduction or the overarching objective to ensure that the IES resid-
ual contamination does not pose an unacceptable risk to human health or the
environment. Emptying the Dounreay Shaft and immobilizing the highly radioactive
liquid raffinate from fuel reprocessing constitute some of the highest risks at Doun-
reay. Good progress is being made in immobilizing raffinates. Built in the 1950s, the
shaft plunges 65.4m below ground. RAW was disposed there until 1977, when an
explosion ended the practice. Shaft emptying will complete in 2025 with final reme-
diation of the shaft and silo area by 2028. The removal of contaminated alkali metals
and immobilization of all MTR liquid raffinate streams has significantly reduced the
overall site hazards. Work continues with residual alkali metal destruction in the PFR
and DFR reactor vessels with all liquid metal residues scheduled for destruction by
2024. Significant hazard reduction is also achieved through the transfer of all spent
nuclear fuels to Sellafield. It is expected the consolidation of exotic fuels from